In accordance with recent increase in integration and capacity of large scale integration (LSI) circuits, the widths of circuit lines required for semiconductor devices have become increasingly smaller. Lithography technique is used to form a desired circuit pattern on a semiconductor device, and pattern transfer using an original drawing pattern referred to as a mask (reticle) is performed in the lithography technique. In order to produce a high accuracy mask used in the pattern transfer, a charged particle beam drawing apparatus having excellent resolution is used.
The charged particle beam drawing apparatus is configured to divide each of a plurality of column regions designated on a target object, such as a mask, into a plurality of stripe regions (frame regions). The stripe regions are further divided into a number of sub-regions to generate shot data. The charged particle beam drawing apparatus then moves a stage on which the target object is mounted in a longitudinal direction of the stripe regions according to the generated shot data, while positioning a charged particle beam by main deflection on each sub-region and shooting the charged particle beam by sub-deflection to a predetermined position of the sub-region.
In such a charged particle beam drawing apparatus, total drawing time is necessary from several hours to several ten hours. In order to recognize the drawing status during the drawing, it is crucial to determine a drawing progress ratio. The drawing progress ratio is calculated using one of expressions including: an expression of dividing the number of drawn shots by an estimated number of shots, an expression of dividing the number of drawn stripes by an estimated number of stripes, and an expression of dividing the number of drawn columns by a total number of columns. The estimated number of shots and the estimated number of stripes are calculated before drawing, and the total column number is included in the drawing data. Herein, the number of shots refers to the number of shots (e.g., the number of figures) of the charged particle beam, the number of columns refers to the number of column regions, and the number of stripes refers to the number of stripe regions.
In practice, however, there is a case where part of data necessary for calculating the drawing progress ratio is not able to be obtained. For example, the estimated number of shots or the estimated number of stripes could be calculated before drawing, but such estimated data may not be acquired due to some reason (e.g., parameter errors or not supporting functions of an estimated data providing module). In this case, the drawing progress ratio is calculated using the total number of columns that can be obtained without fail.
However, the drawing time of the column regions largely differs for each column region. For example, the drawing time of a first column region may be 30 seconds, while the drawing time of a second column region may be 3 hours. In this case, if the drawing progress ratio is calculated by one of the above-described expressions, i.e., the number of drawn columns divided by the total number of columns, the drawing progress ratio is not updated during or until the end of the drawing of the second column region. A resulting drawing progress ratio is significantly different from the actual drawing progress ratio. It is, therefore, desired to obtain a correct drawing progress ratio.